The open-cycle magnetohydrodynamic (MHD) system for generating electrical power has been widely discussed as a possible means of improving fuel energy utilization. In the MHD system, a fuel such as coal is burned in a combustor to provide combustion gases at such high temperatures (2500.degree. K. to 2750.degree. K.) that a plasma is generated. The plasma is seeded with an electrically conductive material, such as a potassium compound like potassium carbonate (K.sub.2 CO.sub.3) to increase the electrical conductivity of the gases. This high-temperature electrically-conductive plasma has pressures of approximately 4-9 atmospheres. The plasma accelerated then into a high linear velocity (0.7 to 2.0 Mach), for example, for passing through an opened ended circumferentially walled MHD channel. Superconductive magnets outside the channel direct high levels of magnetic flux crosswise through and along the channel. The electrically-conductive gases rapidly transverse the magnetic flux and thereby induce on the channel walls parallel to the flux a DC potential that is directly proportional to the conductivity and the speed of the gases and to the square of the magnetic flux, and that is inversely proportional to the pressure of the gases. This DC power in turn is converted to AC power by an inverter or the like for normal transmission to end users.
The combustion gases discharged from the MHD channel will be at temperatures generally exceeding 2000.degree. K. and probably even as high as 2200.degree. K. and at velocities generally exceeding 0.8 to 1.6 Mach. A diffuser is used to convert the kinetic energy into thermal energy by recovering the pressure to atmospheric or slightly higher. Such MHD systems have been disclosed in the Marchant U.S. Pat. No. 4,345,173 issued Aug. 17, 1982 and the Berry et al. U.S. registration no. H410 published Jan. 5, 1988, the disclosures of this patent and statutory invention registration being incorporated herein.
One of the problems encountered in the MHD systems is the exhaust of various gases which are deleterious to the environment. Sulfur oxides, nitrogen oxides as well as carbon dioxide are vented in varying concentrations and each of these gases provide some detriment to the environment. The nitrogen and sulfur oxides contribute to acid rain while the carbon dioxide contributes to the so-called "green house effect".